Comparison of aerosol and climate variability over Germany and South Africa

A radiation‐based model is employed to evaluate seasonal, interannual, and spatial variability within monthly averaged turbidity (the total column amount of aerosol) at eight stations in South Africa and 13 stations in Germany. Germany has a strong seasonal turbidity trend of summer maxima and winter minima. In South Africa the seasonal turbidity trend is weaker, but, on average, turbidity peaks in spring and is lowest in autumn and winter. Over the last several decades, turbidity over Germany has decreased significantly at seven stations. The impacts of the El Chichón and Pinatubo volcanic eruptions are evident in the turbidity signatures over Germany. Four stations in South Africa show long‐term trends in turbidity, but there is no consistent trend. Turbidity in Germany appears to be more influenced by aerosols of non‐local origin than in South Africa, where the aerosol load may be of more local origin. Long‐term monthly averages of Ångström's turbidity coefficient β over Germany range between 0.019 and 0.143, and long‐term annual averages range between 0.064 and 0.116. Over South Africa, turbidity is noticeably lower: long‐term monthly averaged β ranges between 0.004 and 0.071, and the long‐term annually averaged β ranges between 0.013 and 0.047. When averaged across all stations in each of the respective countries, turbidity is, on average, between 2.6 and 5.8 times higher in Germany than in South Africa, depending on the time of year. The climate of South Africa is clearly more humid than Germany, although both countries have strong seasonal trends in humidity. South Africa has become more humid over the last several decades. The decrease in turbidity at stations in Germany appears to be due to a reduction in aerosol emissions and/or changes in climatic factors other than humidity. Copyright © 2003 Royal Meteorological Society